Some Modifications of Gradient Weighted Filters

Gradient weighted filters are locally adaptive weighted mean filters. In this paper, a general formulation of gradient weighted filters with some characteristic parameters was derived first from existing gradient weighted filters. Then we propose some modifications by varying these parameters. We modify gradient inverse weighted filters, characterize filters into first and second order filters, and propose 5 filters. Moreover, an imposed criterion for second order filters to preserve fine details was introduced to promote the existing gradient weighted filters. Finally, a criterion to combine first and second order filters was proposed to remove noise with mixed types. Throughout this paper, rational analysis and experimental results demonstrate the efficiency of the proposed methods. C © 1999 Academic Press